TEST: car_diff error dropdown

[elkoled]

Not for merge. Intentional nissan failure to verify the car_diff comment renders errors in a collapsible dropdown.

🤖 Generated with Claude Code

[github-actions]

Car behavior report

Replays driving segments through this PR and compares the behavior to master.
Please review any changes carefully to ensure they are expected.

Testing 50 segments for: NISSAN_XTRAIL, NISSAN_LEAF, NISSAN_LEAF_IC, NISSAN_ROGUE, NISSAN_ALTIMA

✅ 0 changed, 0 passed, 50 errors

Show errors

Traceback (most recent call last):
  File "/home/runner/work/opendbc/opendbc/opendbc/car/tests/car_diff.py", line 87, in process_segment
    CP, states, timestamps = replay_segment(platform, can_msgs)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/opendbc/opendbc/opendbc/car/tests/car_diff.py", line 78, in replay_segment
    CI.apply(CC, msg.logMonoTime)
  File "/home/runner/work/opendbc/opendbc/opendbc/car/interfaces.py", line 116, in apply
    return self.CC.update(c, self.CS, now_nanos)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/opendbc/opendbc/opendbc/car/nissan/carcontroller.py", line 25, in update
    raise RuntimeError("car_diff error dropdown test")  # TODO: remove, intentional failure to exercise car_diff error reporting
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: car_diff error dropdown test

[elkoled]

Test complete: error dropdown renders in the comment as expected. Closing (intentional failure, not for merge).